Figure 5.

BACE1 overexpression induces specific mitochondrial TCA cycle enzyme lesions. (A,B) SH-SY5Y cells overexpressing BACE1 exhibit reduced lactate usage at levels ≤ 2mM compared to EV cells as demonstrated by (A) reduced repression of ¹⁴C-glucose oxidation (n = 6) and (B) direct OCR when lactate provided as sole substrate (n = 6–11). (C) Pyruvate dehydrogenase activity (PDH) is reduced in BACE1 overexpressing, compared to EV, cells (n = 5). (D) OCR when EV and BACE1 cells provided 2.5 mM pyruvate as sole substrate (n = 5). (E) OCR of EV and BACE1 SH-SY5Y cells when provided with 2.5 mM glucose alone or 2.5 mM glucose + 4 mM glutamine (n = 4–10). (F) direct OCR when 4 mM glutamine provided as sole substrate (n = 8). (G) BACE1, but not mBACE1, overexpression, reduced the enzyme activity of α-KGDH, compared to EV cells (n = 6). (H) IDH activity (NAD⁺ and NADP⁺ isoforms) is reduced by BACE1 overexpression compared to EV cells (n = 4). (I) BACE1 or mBACE1 overexpression has no effect on fumarase enzyme activity, protein levels or specific activity compared to EV cells (n = 7). Values are means ± SEM. ^*p < 0.05; ^**p < 0.01; ^***p < 0.001.